Diamond coatings for micro end mills: Enabling the dry machining of aluminum at the micro-scale

• Published in: Diamond and related materials 2008-03, Vol.17 (3), p.223-233
• Main Authors: Heaney, Patrick J., Sumant, Anirudha V., Torres, Christopher D., Carpick, Robert W., Pfefferkorn, Frank E.
• Format: Article
• Language: English
• Subjects: Aluminum; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Coating; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Cutting tools; Diamond film; Diamond films; Diamond machining; Diamond tools; Dry machining; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Hot filament CVD; Materials science; Mechanical and acoustical properties; Methods of deposition of films and coatings; film growth and epitaxy; Nanocrystalline; Performance enhancement; Physical properties of thin films, nonelectronic; Physics; Specific materials; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2007.12.009

We show that thin diamond coatings can dramatically enhance the performance of micrometer-scale cutting tools. We present a new approach for coating 300 μm diameter tungsten carbide (WC) micro end mills using a tailored seeding method and hot filament chemical vapor deposition (HFCVD) to obtain uniform, conformal, and continuous diamond coatings less than 2 μm in both thickness and grain size. The performance of the uncoated and coated tools has been evaluated by dry machining channels in 6061-T6 aluminum. The test results demonstrate far lower tool wear and breakage, much lower adhesion of aluminum to the tool, and significantly lower cutting forces for the coated tools. The coatings achieve a more predictable surface finish and enable dry machining at high speeds (40,000 rpm) with little or no burr formation. The improved performance of the coated tools is a result of the superior tribological properties of fine-grained diamond against aluminum, specifically low friction, low adhesion, and low wear of the film. Since the coating allows machining without lubricants and essentially eliminates metal burrs, this approach can reduce the environmental impact of micro-machining processes and offers greatly improved performance for micro and meso-scale manufacturing applications.